1. Field of the Invention
The present invention generally relates to a fluidic device, in particular, to a magnetically actuated fluidic device.
2. Description of Related Art
Conventional biochemical reaction experiments are a kind of labour-intensive work. Scientists carry out biochemical reactions on reagents with test tubes and burettes in a lab, mainly for controlling the reagent delivery, mixing a reagent with a checked body, and waiting for a required time to perform a reaction or separation/extraction. A lab of certain scale has already employed mechanical arms to carry out the reactions, so that the labour force is greatly reduced, and the reactions are under precise control. However, the mechanical arm is high in cost, inconvenient to carry, and thus limited in application. Professor Manz from Germany proposed a concept of micro total analysis system (μ-TAS) in 1989, so as to integrate complicated analysis in the lab onto a chip of several centimeters large. That is, the analysis used to be carried out in a lab can be implemented on a microchip, so it is also called lab-on-a-chip, and generally referred to as a microfluidic chip. This chip is widely applied in fields such as medical detection, new drug development, and food inspection.
Microfluidic element and system techniques are mainly directed to control, sense, react, and analyze micro amount of fluid. The key elements include a micro-valve, a micro-pump, a micro-flowmeter, a micro-nozzle, a micro-channel, and a micro-mixer, etc., and those elements can be integrated into intelligent micro-fluidic system chips with various functions. Further, many different methods can be adopted to drive a small amount of (or even a micro amount of) fluid from a storage zone to a mixing region, a reaction zone, an inspection zone, and finally to a waste liquid zone, including syringe and peristaltic pumps, electrochemical bubble generation, acoustics, magnetics, DC and AC electrokinetics, and centrifuge. Four important and feasible methods, namely, centrifuge, pressure, acoustics, and electrokinetics, are compared in the documents.
Pressure and centripetal force are both volume-dependent forces, which scale as L3 (in this case L is the characteristic length corresponding to the capillary diameter). Piezoelectric, electroosmotic, electrowetting, and electrohydrodynamic (EHD) pumping all scale as surface forces (L2), which represent more favorable scaling behavior in the micro domain The above two methods have a broad velocity range, and are used for biochemical analysis for a long time, so their relative equipments and parts are rather mature. The acoustics capable of generating power through the vibration of a solid-liquid interface is complicated in application and still under study.
The electrokinetic must be used with electrodes in contact with a solution. The driving force is related to the ion strength and pH value of the liquid, and is difficult to be widely applied.
The immunoassay employing molecular recognition between antibody and antigen is the most commonly used inspection method at present. Due to its specificity and sensitivity on pathogen inspection, the immunoassay is generally applied to quantitative analysis of substances to be inspected in clinical diagnosis, food inspection, and environmental analysis. The heterogeneous immunoassay is the most widely adopted. In particular, the antibody is usually fixed on a microtiter plate or microbeads. The fixing of the antibody solid phase directly provides a separation effect between the antibody-antigen and the checked body residues, and meanwhile concentrates the subject matter of inspection to a solid phase surface.
The strip immunoassay, known as the lateral-flow immunoassay or immunochromatography, is widely applied in the diagnosis of point-of-care. However, many heterogeneous immunoassays cannot be implemented by means of a strip, and still needs to be handled in centralized laboratories. Besides, the analysis usually lasts for several hours due to the limitation of the quality transmission for diffusion on the microtiter plate. The microfluidic chip can be adopted to reduce the consumption of the samples from 100 mL to 1 mL, and more particularly, greatly shorten the analysis time to tens of minutes. The shortening of the analysis time is caused by a reduction of the diffusion distance from the biomolecules to the solid phase surface, and thus the fluid brings the molecules quite close to the solid phase surface.
The fluid driving force of a microfluidic chip generally comes from external power sources, for example, an electrokinetic flow provided by a high voltage, a pressure flow provided by a syringe pump, or a centrifugation induced flow provided by a mechanical motor. However, these equipments are large in size, high in price, and restrict the microfluidic chip only to be used in the centralized laboratories, so the advantages of the microfluidic chip are greatly weakened. For the application on diagnosis of point-of-care or on-site environmental analysis, a fluid manipulation technique without requiring large external equipments is in urgent need of development. In addition, the microfluidic chip simple in immunoassay and low in cost is the best choice, and more particularly, the microfluidic chip is required to have a single-use characteristic (as such analysis cannot be implemented repeatedly).
Therefore, the above technique should achieve the following efficacies. First, the technique must be able to perform synchronous inspection to obtain similar marker combinations. Further, the technique must be convenient in sampling inspection samples so as to reduce the amount or volume of the samples. In addition, the technique must be employed once to reduce the cost, rapid and simple in operation, and applicable to various kinds of diseases.